Previous hard disk drives (HDDs) typically include devices and/or procedures capable of detecting the occurrence of an error occurring during a read operation (or similar operations such as “verify”). Many previous HDDs also include apparatuses and procedures intended to recover some or all of the data. Recovery can include such items as performing a re-read in the same conditions and/or performing a re-read while altering conditions such as the number of revolutions (i.e., the number the times the re-read is consecutively tried at a given disk location), changing the tracking (such as moving the read head slightly off the nominal track center, i.e. “microjog”) and the like. Other approaches have been used such as error correction procedures and the like.
Although previous error recovery procedures can succeed in recovering data following some read errors, it is believed there is room for improvement in this regard. Accordingly, it would be useful to provide a system method and apparatus which can efficiently and effectively recover at least some data following detection of a read error.
Some HDDs include the capability of changing or adjusting the fly height of the read head (the distance of the read head from the adjacent section of the disk). Although there have been proposals for changing fly height in connection with error recovery, it is believed there is room for improvement in this regard. Accordingly, it would be useful to provide a system, method and apparatus which uses fly height adjustment to achieve efficient and effective data recovery.
In at least some situations, it is substantially convenient or efficient to provide for error recovery procedures which consume a limited and/or known amount of time or computation or other resources. Accordingly, it would be useful to provide an error recovery system, method and apparatus which is not only effective and efficient, but also is short and/or determinant with respect to the amount of time (or maximum amount of time) or other resources required.